ECG ECG Pharmacology and Cardiac Medications 2 — Questions and Answers
Question 1: Hypokalemia from loop diuretic use (e.g., furosemide) produces which characteristic ECG change?
- Peaked T waves and narrow QRS
- Flat or inverted T waves and prominent U waves (Correct answer)
- Shortened QT interval
- Elevated J-point with delta waves
Correct answer: Flat or inverted T waves and prominent U waves
Hypokalemia flattens or inverts the T wave and causes prominent U waves (deflection after the T wave) due to delayed ventricular repolarization.
Question 2: A patient receiving IV procainamide (Class IA) for ventricular arrhythmia may develop which dangerous ECG pattern?
- PR shortening
- QRS widening greater than 50% of baseline (Correct answer)
- ST elevation in all leads
- Inverted P waves in lead II
Correct answer: QRS widening greater than 50% of baseline
Procainamide can widen the QRS by more than 50% of the baseline width, signaling toxicity and increased risk of proarrhythmia.
Question 3: Which ECG finding would suggest a patient has received too much atropine?
- Bradycardia with prolonged PR interval
- Sinus tachycardia with shortened PR interval (Correct answer)
- Wide QRS and prominent U waves
- Complete AV block
Correct answer: Sinus tachycardia with shortened PR interval
Atropine blocks muscarinic receptors, increasing SA node automaticity and speeding AV conduction, resulting in sinus tachycardia with a shortened PR interval.
Question 4: Tricyclic antidepressant (TCA) overdose is classically recognized on the ECG by:
- Shortened QT interval and slow heart rate
- Widened QRS, right axis deviation, and prolonged QT (Correct answer)
- Peaked T waves and shortened PR interval
- Inverted T waves in lateral leads only
Correct answer: Widened QRS, right axis deviation, and prolonged QT
TCA overdose causes sodium channel blockade (widened QRS), potassium channel blockade (prolonged QT), and rightward axis shift, which is a life-threatening combination.
Question 5: Heparin and warfarin are anticoagulants that do NOT directly alter the ECG. Which ECG change may appear indirectly if anticoagulation reverses a pulmonary embolism?
- Resolution of the S1Q3T3 pattern (Correct answer)
- Development of peaked T waves
- New delta waves in V1-V3
- Shortened QRS duration
Correct answer: Resolution of the S1Q3T3 pattern
A pulmonary embolism can produce the S1Q3T3 pattern; successful anticoagulation and clot resolution can lead to normalization and disappearance of this pattern.
Question 6: Sotalol (a Class III antiarrhythmic with beta-blocking properties) increases the risk of torsades de pointes primarily because it:
- Shortens the QT interval excessively
- Prolongs the QT interval (Correct answer)
- Widens the QRS complex beyond 200 ms
- Suppresses P wave formation
Correct answer: Prolongs the QT interval
Sotalol prolongs ventricular repolarization (QT interval), creating a vulnerable window for torsades de pointes, a polymorphic ventricular tachycardia.
Question 7: An ECG technician notices a patient's rhythm strip shows bradycardia and first-degree AV block. Which medication history is most consistent with these findings?
- Nitroglycerin
- Metoprolol (beta-blocker) (Correct answer)
- Aspirin
- Warfarin
Correct answer: Metoprolol (beta-blocker)
Metoprolol, a beta-blocker, reduces heart rate and slows AV node conduction, commonly producing bradycardia and a prolonged PR interval (first-degree AV block).
ECG ECG Pharmacology and Cardiac Medications 2
Hypokalemia from loop diuretic use (e.g., furosemide) produces which characteristic ECG change?